Solenoid

Magnetic field seeks the path of minimum reluctance, like an electric current seeks the path of least resistance. The disinclination and resistance are associated. Resistance refers to the opposition to current flow in the circuit. The reluctance relates to the opposition to the flow of the magnetic field. Lower reluctance, the more the attraction of the materials of the magnetic field.

The solenoid is a device that uses these principles. Spiral coil of wire produces a magnetic field. Iron core fits loosely in the coil of wire. When the current is switched off, the kernel is beyond the scope of the coil. When current is applied, the kernel gets into the heat exchanger. This is called the effect of sucking spiral (see Fig. 6-17).

Sucking effect is often used in devices that require a small amount of movement. One type of solenoid shown in Fig. 6-18. A common use for the solenoids in a device called solenoid valves (see Fig. 6-19). It is a device that opens and closes to allow the flow of liquids or gases. In the majority of valves, for example, you turn the handle or knob to start or stop the flow of gas. Solenoid valves are used as safety devices. They are gas lines, air lines, and pipelines. Many species are used for air conditioning, cooling and heating).

Solenoid valve is shown in Fig. 6-19 is closed when there is no current through the coil. The valve stem is held closed by a spring with regard to the pressure of light. When the valve is closed, the gas can flow. Current is applied when a person or the thermostat switches the heating. The current draws movable core or plunger spool. This opens the gates for gas flow. When the current is switched off, the spring moves the valve system back into the closed position.

The same principle is widely used in the solenoid relay type. Asolenoid the relay as an electric switch. Coil in this type of relay and pulls the major part that has a number of electric contacts. Contacts are designed so that they can or disconnection of electrical circuits. The contacts may themselves be designed to handle large amounts of current. But coil control solenoid can only operate on a fraction of an ampere. The effect is that for low-voltage, low electrical current is used to control the flow of large amounts of power.